INTRODUCTION. xvi
Experiments in animals have not accomplished so much
for the elucidation of the reparative processes of bone in
man as might probably have been expected. he eir-
eumstanecs attendant on the fraetured or necrosed bone,
in man, are essentially different from those of the experi-
ment of breaking, or causing the death of a bone in ani-
mals. Thus, around the fractured bone of an animal, the
deposit of cartilaginous and osseous substance, whieh has
been designated provisional eallus, is of uniform oeeur-
renee. But, in the human subject, no sueh eartilaginous
and osseous deposit uniformly takes place around the
fractured bone; here, therefore, it is not an essential part
of the reparative proeess. Also, with respect to the produe-
tion of neerosis by experiment in animals, the condition of
the surrounding soft parts is so materially different from
the eondition of these parts preceding and aeeompanying
the death of the shaft of a bone in man, that, in eonse-
quenee, the features of the reparative process in the two
eases are essentially different. It has, therefore, been
incorrectly assumed, that beeause sueh is the reparative
process of fraeture, or necrosis, in animals, it must be so
likewise in man.
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